This invention relates to loadbearing supports and in particular to workunits or workbenches.
A recent development in collapsible and portable workbenches has excited the enthusiastic interest of professional and home craftsmen throughout the world and has earned unprecedented acceptance because of its great and manifold utility. This development is represented in several patents including U.S. Pat. Nos. 3,615,087 and 3,841,619 and also in British Pat. No. 1,422,521. A related development is illustrated in German Offenlegungsschrift 2,540,000 dated Apr. 1, 1976.
Without detracting from the success of previous designs such as these shown in these specifications, we have found that, by careful redesign, certain aspects of the bench can be improved and at the same time certain economies made in manufacture.
According to one aspect of the present invention a load bearing support comprises a top structure, and a collapsible supporting structure which includes a pair of generally flat frames pivotally connected to the top structure for swinging movement between a collapsed position in which at least portions of the frames and the top structure lie close together, and an erected position in which the frames support the top structure on four feet above the ground. The supporting structure also includes four retractable extensions, two of which are mounted on one of the frames and the other two are mounted on the other of the frames. The extensions can be moved between an extended position in which feet of the extensions contact the ground, and a retracted position in which, whether the frames are collapsed or erected, each pair of extensions lies generally within the frame to which the pair of extensions are connected. The top structure is supported at a first height above the ground when the frames are erected and the extensions are extended, and is supported at a second, lesser, height above the ground, when the frames are erected and the extensions are retracted. Collapsing and erecting of the frames is possible whether the extensions are retracted or extended.
Each retractable extension, when in its extended position, preferably lies substantially in the same plane as the frame on which it is mounted.
When the retractable extensions are in their extended positions, their ground-engaging feet may be spaced apart in the direction parallel to the axes of swinging of the frames by a distance greater than the spacing in the same direction of the feet on the frames which engage the ground when the extensions are in their retracted positions. Each retractable extension may comprise a leg which is pivotable between the retracted position, in which it lies generally parallel to the axes of swinging of the frames, with its ground-engaging foot inboard of its other end, and the extended position, in which it extends obliquely outwards and downwards from the frame on which it is mounted. Preferably each retractable extension leg is provided with a tension toggle spring acting to hold it in whichever of its retracted and extended positions it has been placed.
Each frame may comprises a pair of legs connected, adjacent their ends remote from the top structure, by a horizontal bar, and the retractable extensions may be mounted on the horizontal bar of each frame. Each horizontal bar may comprise a channel whose opening faces downwards when the support is in its erected position, and the retractable extension legs are of such a cross-section that they can be received substantially behind at least one of the limbs of the channel, and are pivotally connected to the channel at their ends remote from their ground-engaging feet. When the retractable extension legs are in their retracted positions, their ground-engaging ends overlap. For simplicity of assembly and disassembly, the horizontal bars may be readily detachable from the legs of its frame.
According to another aspect of the invention a load bearing support comprises a top structure, and a collapsible supporting structure which includes a first generally flat frame and a second generally flat frame, each pivotally connected to the top structure for swinging movement about first and second pivot axes, respectively. The frames can be folded to a collapsed position in which the first frame lies on the same side of the second frame as does the top structure, and the frames and the top structure lie close together. The frames can also be unfolded to an erected position in which the frames support the top structure above the ground, with the frames diverging from one another in the downward direction. The supporting structure also includes at least one link whose ends are connected to the first and second frames for pivoting relative thereto about third and fourth pivot axes, respectively. When the support is in its erected position, the third and fourth axes lie at a lower level than either of the first and second pivot axes, and the third pivot axis lies at a level which is sufficiently below the level of the fourth pivot axis that the sum of the distances between the first and second pivot axes and between the first and third pivot axes is substantially equal to the sum of the distances between the second and fourth pivot axes and between the third and fourth pivot axes. This arrangement enables both the first and fourth pivot axes to lie close to the plane joining the second and third pivot axes in the collapsible position of the support. When the support is in its erected position, the second pivot axis lies at a level which is sufficiently lower than the level of the first pivot axis that, assuming that the attitude of the top structure is not changed from its erected position, the second frame can lie substantially horizontal in the collapsed position of the support. The first-mentioned sum of distances may be slightly greater than the second-mentioned sum of distances to enable the frames to lie substantially parallel to one another in the collapsed position of the support.
According to a specific construction at least the second frame includes a pair of legs, and the associated end of each link lies adjacent one of the legs, on the side of that leg closest to the other leg of the pair. The legs of the second frame may be connected, at their ends remote from the second pivot axis, by a horizontal bar. Each link may deviate from the straight line joining the third and fourth pivot axes, at least over the part of its length which lies adjacent the horizontal bar in the collapsed position of the support. The deviation is an upward deviation when seen in the erected position of the support.
Preferably the supporting structure also includes means for locking the support in its erected position. This locking means may comprise a folding linkage at each end of the supporting structure, comprising two parts connected by a pivot. The ends of each linkage are pivotally connected, respectively, to the second frame and to the top structure, and the axes of the pivotal connections at the ends of each linkage coincide with the first and fourth pivot axes.
Preferably, as the support is moved from its collapsed to its erected position, each folding linkage moves through a position in which its three pivots are co-linear, and shortly afterwards reaches a position in which further relative pivoting of the two parts of the linkage is prevented. Each folding linkage may be fitted with an overcenter action spring acting to hold the linkage in its erected position.
With the support in its erected positions, the frames preferably diverge in the downward direction to place their feet outside the worktop plan.
For convenience of manufacture, when the support is erected, the first and second frames lie at equal but opposite angles to the vertical. A possible alternative is for the frames to lie at different angles from the vertical, in particular so that the user can easily stand on a horizontal bar on the frame having the greater inclination either for sawing a workpiece, or for climbing on to the top structure. Also the user can place his foot on the horizontal bar for stabilizing the bench at either height.
The top structure may afford a working surface which lies horizontal when the support is erected, and lies generally parallel to the frames when the support is collapsed, whereby the support forms a workbench; and preferably the working surface is formed by a pair of elongate vise beams, one of which is movable relative to the other in directions parallel to the plane of the working surface and generally transverse to the length of the vise beams, to clamp a workpiece between adjacent edges of the vise beams. The movements of the one vise beam are produced by operation of one or both of a pair of independently operable clamping devices spaced along the length of the vice beams, whereby the gap between the vice beams may be made to taper along the length of the vice beams. The one vice beam is restrained against rocking about axes parallel to its length in response to the reaction force exerted by a workpiece on the one vise beam when the workpiece is gripped by the vise beams. Moreover, the top structure may include a pair of elongate supports which extend below and transversely to the length of the vise beams, one near each of the vise beams, and on which the vise beams are mounted. The first and second frames are pivoted to these elongate supports. In order to be able to clamp downwardly extending workpieces such as a door, the vise beams preferably project at their ends beyond the elongated supports for the vise beams.
According to yet another aspect of the present invention a workunit comprises a top structure having an upwardly facing supporting surface. A supporting structure is connected to the top structure and includes front and rear generally flat frames pivoted at their upper ends by front and rear pivotal connections to the top structure for movement between erected and collapsed positions. The front and rear pivotal connections are disposed adjacent the front and rear of the top structure respectively, and the frames, as viewed in side elevation when erected, are downwardly and outwardly splayed and rest on pads, which in the erected position can engage the floor at points forward and rearward respectively of a plan projection of the top structure. The frames, when folding from the erected position to the collapsed position, each move in the same rotary direction with respect to the top structure, with one frame leading the other, trailing, frame during such rotation. The frames are interconnected by rigid cross-ties, one at each end, which are pivoted to the frames by further pivotal connections, of which the pivotal connection to the leading frame is substantially lower on the frame than the pivotal connection to the trailing frame. During collapsing, the trailing frame approaches the leading frame and, in the collapsed position, at least part of the trailing frame lies close to the leading frame.
According to a further aspect of the present invention a combined workbench and sawhorse includes a top structure, a pair of front legs and a pair of rear legs for supporting the top structure at sawhorse height. Each pair of legs is interconnected adjacent its lower end by a horizontally extending strut. A pair of front lower legs and a pair of rear struts, and rear lower legs are pivoted respectively to the front and have retracted positions and extended positions, in the latter of which they position the top structure at workbench height. Below its pivotal connection to the strut, each lower leg, in its extended position, has a portion which abuts a thrust surface positioned on the main leg or the strut.
Conveniently, each lower leg is pivoted to one of the struts closely inboard of the connection of the strut to the main leg. In one arrangement the thrust surface is positioned adjacent the lower end of the main leg. Alternatively, the thrust surface may be afforded by a strengthening member secured to the inboard face main leg. In order to assist in obtaining complete front to back stability there may be additional thrust faces secured to the main leg or strut which lie close to or in contact with front and rear faces of the lower leg when erected.
In one construction the thrust surface and the additional thrust faces for each lower leg are formed on a block connected to the inboard face of the adjacent main leg. Alternatively, the thrust surface and the additional thrust faces for each lower leg are formed on a single sheet metal pressing. In a further construction the strengthening member carried a conical peg which engages in a circular aperture in the outboard side face of the lower leg.
Each horizontally extending strut may be a downwardly opening U-shaped channel having a pair of depending limbs and a top interconnecting web. Each lower leg may be pivoted to one of the struts by a bolt extending through each of the limbs of the U-shaped channel. Preferably each lower leg has, in the extended position, an upper portion above the pivot. Front and rear faces of the upper portion lie close to or in contact with the inside faces of the limbs of the U-shaped channel, and the front limb of the U-shaped channel may have a horizontal stiffening bead. The web of the U-shaped channel may form an upwardly facing step on which, when the lower legs are in their extended positions, a user can stand at an elevated height above the floor with the worktop at sawhorse height with respect to the user. For this purpose portions of the said web may be raised or grooved to form non-slip, foot gripping surfaces.
Each lower leg may be provided with a spring which tends to maintain the lower leg in its extended position. Preferably a spring is included for each lower leg tending to maintain the lower leg in its raised position. Conveniently the springs are one and the same and may be arranged to be stressed to go overcenter in bistable fashion during passage between the retracted and extended positions and vice versa.
In order to maintain a stable construction each lower leg, in its extended position, preferably lies in a plane containing its adjacent main leg but extends laterally to the side of that leg whereby the floor contact area of the lower legs is greater than the floor contact area of the main legs, extending therebeyond both forward and rearward, and on both sides.
In a specific embodiment the lower legs of each pair overlap one another in their retracted position and one lies partially above the other. Conveniently either lower leg of a pair can be raised first. Each lower leg may have a stud projecting from it to facilitate its movement manually between the retracted and extended positions.
In an alternative construction the horizontally extending strut, in the form of a U-shaped channel has an end plate at each end connected between the front and rear limbs of the channel. The end plate may be a folded part of one limb of the U, and the thrust surface may be integral with the folded part.
An alternative embodiment, not of a dual-height nature, has its four main legs projecting downwardly beyond the horizontal struts or bars by an amount substantially equal to the differential between normal workbench and sawhorse heights. `Workbench height` may be between 29" and 34" and `sawhorse height` may be between 18" and 25".
Construction of the type described can be made much more cheaply and quickly and with less expensive production equipment than those described in the prior patents referred to above. They have the great merit of simplicity, lightness, and ease of erection and folding. Nevertheless, when erected, the top structure, frames and links provide a very rigid six sided box-like construction with each side of the box forming a rigid diaphragm capable of resisting shear loads.